The present invention relates to a method of manufacturing electric machines including motors and generators using kinetic spraying metal forming. More specifically, the present invention is directly related to a method of manufacturing both conductive metallizations, as well as permanent and soft magnets by applying highly-defined, high-velocity sprays of conductors and magnetic materials in powder form to an appropriate carrier without the need for additional molding, shaping, sintering or tooling steps.
Description of the related arts “Electric machines” in the broadest sense, are fabricated from specialized arrangements of conductive coils, magnetic materials, supporting structures, and ancillary components such as fasteners, wires, and other conductors.
Most “permanent” magnets and some “soft” magnets are produced through a molding and sintering operation from an admixture of magnetic materials and appropriate binders in an initially powdered form, wherein the final shape of the particular magnet is dictated by the mold tooling used. Additionally, “permanent” magnets must be magnetized by exposing the magnet to sufficiently high magnetic fields so as to introduce a strong, semi-permanent magnetic alignment of individual magnetic dipoles and larger physical domains. “Soft” magnetic materials, usually predicated on iron and several of its alloys, are often fabricated from sintered powders or laminated sheets, produced such that the intrinsic magnetic moment for the material is not permanent, but rather is determined by the magnitude of the applied field. Coils made predominantly from copper wire are used both to generate magnetic fields and electromagnetic torque in the airgap, with the ultimate goal to generate motion, as in an electric motor, or to generate electric power as in a generator or alternator. Electric machines, which may be either generators or motors, are thus assembled from specific geometric arrays of coils, magnetic materials and supporting structures or carriers. Assembly processes for electric machines involve attachment of magnets, laminations and coils to housings designed to receive the magnet. When multiple magnets are assembled, it becomes difficult to precisely align and attach each magnet to the article or housing. A process that eliminates the molding, hardening and assembly steps greatly simplifies the construction process and reduces the cost and complexity of the resultant article. Moreover, by supplying the constituent materials of the particular electric machine as “coatings” in contrast to separate three-dimensional structures, it is possible to realize new and different electric machines, fabricated by an unconventional process onto heretofore unused carriers or platforms.
It is possible to thermal spray magnetic materials onto a carrier as described in U.S. Pat. No. 5,391,403 ('403). This thermal spray process has been used where relatively weak magnetic fields are sufficient such as for use in a sensor. The method described in the '403 patent is capable of producing very thin magnetic coatings between 100–200 μm in thickness. This coating was made from magnetic oxides of iron, cobalt and nickel. The intense heat from the thermal spray process causes the base metals to oxidize and produce oxides. The oxides produce much weaker magnetic fields than the base metals from which they originate. They lack the capacity to produce sufficiently strong fields required for motors and generators. The present invention is directed to a method of producing magnets from base metals that are capable of producing strong magnetic fields.
U.S. Pat. No. 4,897,283, teaches a method of producing aligned permanent magnets by a high temperature plasma thermal spray of samarium-cobalt. Auxiliary heat is applied before, during and after the thermal spray to produce the magnet. Because the deposition is conducted in an environmentally-controlled chamber, oxidation of the metallic alloy is expected to be minimal. Masking is optionally used to produce fine deposition features, as is well-known in the thermal-spray art. The temperature needed to produce the plasma spray degrades the magnetic properties of the resulting article.
Thermal spray has the advantage of being capable of rapidly producing a layer of bulk material atop a carrier, but the heat needed to create the molten metal droplets can alter the magnetic properties of the sprayed material. Another family of thermal spray technologies that does not use high temperatures for producing molten droplets is collectively known as kinetic spraying. One kinetic spray technique predominantly used to date has been that of cold gas-dynamic spraying or “cold-spray”. The technique described in U.S. Pat. No. 5,302,414 incorporated herein by reference, ('414) uses a nozzle whose acceleration and focusing properties are determined by gas dynamics and geometry to produce a jet of solid or semi-solid particles that impinge onto a deformable substrate material, typically metal. The particles have a size range of approximately 1–50 micrometers. The particles are introduced under pressure into a supersonic gas stream created through use of a converging-diverging (deLaval) nozzle. The particles, once accelerated to near supersonic velocities, impact on a collecting substrate where they form a thick deposit, by a process believed to be similar to explosive compaction or mechanical plating. The coating may be applied for a number of purposes such as corrosion or wear resistance. The '414 patent, states that the application method may be used for electrically or magnetically conducting coatings. However, the '414 patent does not provide examples of electrically or magnetically conductive coatings. The methods described all produce very thin (<400 μm) coatings. These coatings are generally too thin to be of use as magnets such as those typically found in electric machines. The present invention is directed to the application of bulk material to produce magnets capable of creating magnetic fields useful in motors, generators and similar devices.
The invention described herein utilizes the “cold spray” process to produce electric machine elements as “coatings” or deposits on an appropriate substrate or carrier. While the '414 patent discloses electrical and magnetic materials, it does not provide for a methodology for permanent magnet deposits, composite magnets, deposition conditions, properties of soft magnetic materials, or suggested geometries for planarized or ‘coating-based’ electric machines.